1. Field of Invention
This invention relates to spring units and more particularly to spring units for beds, divan beds, mattresses, and other upholstery units. Such beds etc will be hereinafter referred to as xe2x80x98sprung unitsxe2x80x99.
2. Description of the Related Art
Sprung units are conventionally made in differing degrees of hardness, this usually being achieved by varying the number of springs per unit areaxe2x80x94generally known as xe2x80x98the spring countxe2x80x99xe2x80x94of the sprung unit, or by changing the gauge of the wire from which the springs are made. Such variation in the manufacturing procedure, i.e. the incorporation of differing numbers of springs or changing the wire gauge, complicates the manufacturing procedure and consequently increases the manufacturing costs.
It has previously been proposed to incorporate a second spring within a first spring so as to form a double spring unit whereby the springs are compressed in stages so as to lessen the shock on the sprung unit when a person sits or lays upon the sprung unit, Examples of such spring units are shown and described in U.S. Pat. Nos. 1,192,510 (Fischmann), 3,031,690 (Ramsey), and 2,631,840 (Bugenhagen). However, in such previous proposals, the second spring has been connected, either directly or indirectly, to said first spring such that the second spring has not been freely movable within said first spring, which places restrictions on the sprung unit in use.
The present invention therefore seeks to provide an improved form of spring unit which will obviate the disadvantages of known spring units.
According to the present invention there is provided a spring unit for incorporation into a bed, divan bed, mattress, or other upholstery unit comprising a first spring and a second spring located within said first spring, said second spring having no connection to said first spring so as to be freely movable within said first spring.
Preferably, the length of said second spring will be less than that of said first spring.
In an embodiment of the invention, the first spring may be a pocketted spring, and in an alternative embodiment of the invention the second spring may be a pocketted spring. In yet a further alternative embodiment, each of said first and second springs may be pocketted springs.
The pocket of the or each pocketted spring may be composed of a woven material such as calico which is sewn in order to form the pocket(s). Alternatively, the pocket(s) may be composed of synthetic material which is sewn or sonic or heat welded in order to form the pocket(s). Where both springs are pocketted springs, both pockets may be composed of a woven material or both may be composed of synthetic material, or the pockets may be formed one of each material, the pocket of woven material preferably being around said first spring.
According to another aspect of the present invention there is provided a sprung unit incorporating a plurality of spring units, each of said spring units comprising a first spring and a second spring located within said first spring.